| Two-dimensional layered materials have excellent electrical,mechanical and optical properties,atomic-level thickness,and no dangling bonds on the surface.Therefore,they are widely used in the research of nanoelectronic devices and optoelectronic devices.It is the future of high-performance devices.provides new ideas.The tunneling conduction process breaks the rules and restrictions of classical mechanics,and carriers can conduct electricity through high potential barriers,which has played an important role in modern electronics and optoelectronics.Band structure engineering plays a decisive role in tunneling devices.Since two-dimensional materials have abundant energy band structures,continuously adjustable thickness,and arbitrary stacking without considering lattice matching characteristics,people can fabricate according to the designed energy band structure.Two-dimensional heterojunction tunneling device.At present,there are few studies on 2D heterojunction tunneling devices,and they focus on the exploration of device process parameters.The exploration and design of tunneling device principles are still insufficient,and the transport mechanism of tunneling devices is still unclear.In this paper,the construction principle of tunneling sensor is proposed;the tunneling strain sensor of nanocrystalline graphene is prepared,and its strain sensing performance and tunneling mechanism are studied;two-dimensional layered semiconductors（2DLSs）/hexagonal Boron Nitride（h-BN）/multilayer graphene（MLG）tunneling photodetector are constructed.,the relationship between photodetection performance and energy band structure,tunneling layer thickness,etc.was studied;Sn S2/h-BN/MLG tunneling was constructed Floating gate memory,its photoelectric write-erase performance and working mechanism are studied.Nano-graphene single crystals and continuous films were prepared on dielectric substrates by plasma enhanced chemical vapor deposition and chemical vapor deposition methods.As characterized by Raman spectroscopy,scanning electron microscopy,and atomic force microscopy,a three-dimensional growth model on the dielectric substrate is obtained.Strain sensors with different continuity of nanographene were constructed,and the relationship between the sensitivity of the strain sensor and the degree of continuity was studied.The graphene nanometers with a growth time of 25 min had the best uniaxial strain sensitivity.The GF value under tensile strain and compressive strain reached 139 and 68,respectively.The electrostatic control ability obtained from the transfer curve proves that the film is composed of discrete graphene nanocrystals.In the output curve of the nanographene,the current increases exponentially with voltage,and the output current first decreases and then increases with the decrease of temperature.These proves the tunneling conduction process.Through calculation derivation,it is found that when the tunneling type is converted from direct tunneling to FN tunneling,GF will be significantly enhanced;when the source-drain voltage keeps increasing,direct tunneling will gradually switch to FN tunneling,which further leads to an increase of the GF value of the strain sensor.By constructing a 5×5 strain sensor array,the detection of spatial strain is realized.Summarize and verify the mechanism of the influence of the energy band structure on the detection performance of the metal-insulator-semiconductor heterojunction photodetector.The introduction of insulator layer in the device successfully controlled the dark current（<1 p A）of the device,proving the successful suppression of dark current.It is found that Sn S2 with the lowest hole tunneling barrier and the largest electron barrier exhibits the best photodetection performance,which is the same with the as expected results from the energy band engineering.By calculating the energy band structure of the heterojunction,the relationships between the tunneling distance and the thickness of the tunneling layer,the source-drain voltage,and the hole barrier are summarized.It is found that the extremely small hole barrier of Sn S2 makes it has lower tunneling type switching voltage and faster tunneling distance drop speed.The detection performance of Sn S2/h-BN/MLG photodetectors with multiple tunneling layer thicknesses is studied.It is found that the increase in the thickness of the tunneling layer has an obvious inhibitory effect on the dark current.The dark current gradually decreases,while the photocurrent does not change significantly at first and then decreases.Therefore,the responsivity,detectivity,and optical switch ratio first increase and then decrease with the thickness of the tunneling layer.The photodetector with 30 nm thick h-BN simultaneously shows high responsivity of 14A/W,high detectivity of 5.1×1013 Jones and excellent optical switch ratio of 2.5×105.The EQE value reaches 147%under the low working voltage of-0.4 V.This photodetector is successfully applied in single-pixel imaging and a clear image was obtained.A new method of low optical writing energy multibit optoelectronic memory has been developed.The Sn S2/h-BN/MLG floating gate memory is constructed,and the gate voltage is adjusted to generate the on and off states.The off state has extremely low current(<10-12 A),and the current increases to 10-6 A in the on state.The switching ratio reaches 2×106,and this device shows excellent tolerance.By controlling the writing light intensity and writing time,the optical writing multi-level storage function was realized.The minimum writing power of pulsed light is 0.32 n W,the shortest pulse time is 0.05 s.And the energy of a single optical writing is only 1.6p J,which is the lowest value of optical memory based on two-dimensional materials so far.This paper has studied the law of carrier tunneling in the two-dimensional van der Waals heterojunction and its influence mechanism on the sensing performance of the device in detail,which provides a deeper theoretical basis and research direction for the development of high-performance two-dimensional tunneling sensor devices. |
